Hadronic-Origin TeV gamma-Rays and Ultra-High Energy Cosmic Rays from Centaurus A

TL;DR

This paper proposes a hadronic model for TeV gamma-rays and ultra-high-energy cosmic rays from Centaurus A, explaining high-energy photon production via p-gamma interactions and consistent with cosmic ray observations.

Contribution

It introduces a hadronic interaction model for TeV gamma-rays and cosmic rays from Centaurus A, extending beyond the leptonic SED explanation.

Findings

TeV gamma-rays can be explained by neutral pion decay from p-gamma interactions.

The model is consistent with Pierre Auger cosmic ray detections from Cen A.

Predicted neutrino flux is too faint for current detectors.

Abstract

Centaurus A (Cen A) is the nearest radio-loud AGN and is detected from radio to very high energy gamma-rays. Its nuclear spectral energy distribution (SED) shows a double-peak feature, which is well explained by the leptonic synchrotron + synchrotron self-Compton model. This model however cannot account for the observed high energy photons in the TeV range, which display a distinct component. Here we show that ~ TeV photons can be well interpreted as the neutral pion decay products from p-gamma interactions of Fermi accelerated high energy protons in the jet with the seed photons around the second SED peak at ~170 keV. Extrapolating the inferred proton spectrum to high energies, we find that this same model is consistent with the detection of 2 ultra-high-energy cosmic ray events detected by Pierre Auger Observatory from the direction of Cen A. We also estimate the GeV neutrino flux from the same process, and find that it is too faint to be detected by current high-energy neutrino detectors.